Planet 9

downshift · #81 05-11-2009, 09:52 AM

Originally Posted by Rockster

One particularly bad gas is Nox. Nitrogen oxide. If forms in the high temperatures of combustion. To keep this temp down engines are designed to under some operating conditions to allow some mixing of exhaust gases with the fresh incoming charge. Intake and exhaust valve overlap is one such way.

A side effect is some of the cloud and some exhaust gases can flow back into the intake ports and leave deposits on the intake valves. Since fuel injectors are no longer spraying fuel on these surfaces there's nothing to wash these deposits off.

The intake sides of the intake valves are crucial to the proper flow and swirling of incoming air to form the pre-cloud around the spark plug/fuel injector into which fuel will be injected.

Deposits on these intake valve surfaces will affect the proper formation of this cloud and in fact likely lead to even more deposits as the cloud ventures outside of its intended area of existence.

I've been following this thread in the hopes that there would be more discussion on exactly how this carbon gets there in the first place. The closest I've seen is this quote, above.

In order for carbon to form on the intake valves as shown in the pictures, some of the intake cloud and/or exhaust would have to flow backwards, into the intake tract. Rockster mentions that this is deliberate, to keep combustion temperatures down. Valve overlap is the mechanism by which this occurs.

If the intake valve remained open for a bit during the beginning of the compression cycle, a little bit of the intake charge would go back up the intake tract. This would certainly cause carbon build-up on the intake valves, but would negate any varioram effect of the intake tract (where the momentum of the intake charge is used to overfill the cylinders). You would also lose considerable precision on the fuel charge for the next intake cycle, and this precision is one of the main advantages of a DFI engine. The other way you could reverse the flow would be to have the intake valve open at the very end of the exhaust cycle. This would allow some exhaust to flow back up the intake. This would really negate any ram effect in the intake tract, as the intake cycle is the next cycle in the sequence. The only cycle I've left out is the power cycle, and the intake valve can't be open then, for obvious reasons.

In short, I don't see using valve overlap to deliberately reverse the flow as being effective. There are better ways, with fewer repercussions, to keep combustion temps down. Unless I'm missing something, which is certainly possible (probable?)...

But once the carbon is on the intake valve, the only way I see to remove it is something like SeaFoam in the intake tract. Hard running can help clean exhaust valves, as they get really hot, and combustion chambers for the same reason, but hard running doesn't heat up intake valves the way it does exhaust valves. On the other hand, in a DFI engine, the intake valves are not getting cooled with fuel on each cycle...

DFI

Direct Fuel Injection (DFI), is a new technology that Porsche states can cut fuel consumption by up to 15 percent, while increasing power by up to 13 percent. DFI cuts emissions by warming up the catalytic converter more quickly, and ensures a sharper throttle response. Better for your right foot - and the planet, then.

DFI allows much more precise measurement of fuel supply and injection at pressures up to 120 bar; it has numerous combustion modes, with different cycles for cold-starting, low-speed driving and performance driving.

As the name suggests, DFI injects fuel directly into the individual combustion chambers, instead of the intake manifold. The injector valves have an electromagnetic mechanism that controls each injection with astonishing precision, while a high-pressure pump provides the necessary pressure—up to 1,740 psi—to accompany the rapid fire of the fuel injection.

Precise geometry of the injector’s position and its spray pattern is a key factor in helping to improve power, torque and emissions of the engines. The specific placement of the fuel as it enters each chamber creates a swirl that improves the air/fuel mixture, and therefore the overall combustion process.

At engine speeds up to 3500 rpm, a double-injection process is used. In this mode, the required fuel volume is delivered in two successive injections per working stroke. The resulting benefits include faster catalyst warm-up and increased torque in the upper load range.

By forming the air/fuel mix directly in the combustion chamber, DFI contributes to engine cooling. As a result, it is possible to increase the compression ratio and with it the power and efficiency of the engine.

The direct injection process is continuously adjusted. The engine management system reads changes to throttle inputs and performance requirements and, as you drive, the air/fuel mix is monitored and adapted as required. Oxygen sensor circuits within the exhaust system provide accurate emissions control.

Pint of Brew · #82 05-12-2009, 04:35 AM

Just a little tidbit: DFI has trouble with cold-start because the pump has to crank up the fuel rail to an unusually high pressure. This doesn't say much about the engine, however. More about something we already knew:

Pumps that have to pump a very high differential pressure at zero notice with very low temperatures may perform badly.

Do not miss-interpret this reluctance as a combustion error.

DFI

Direct Fuel Injection (DFI), is a new technology that Porsche states can cut fuel consumption by up to 15 percent, while increasing power by up to 13 percent. DFI cuts emissions by warming up the catalytic converter more quickly, and ensures a sharper throttle response. Better for your right foot - and the planet, then.

DFI allows much more precise measurement of fuel supply and injection at pressures up to 120 bar; it has numerous combustion modes, with different cycles for cold-starting, low-speed driving and performance driving.

As the name suggests, DFI injects fuel directly into the individual combustion chambers, instead of the intake manifold. The injector valves have an electromagnetic mechanism that controls each injection with astonishing precision, while a high-pressure pump provides the necessary pressure—up to 1,740 psi—to accompany the rapid fire of the fuel injection.

Precise geometry of the injector’s position and its spray pattern is a key factor in helping to improve power, torque and emissions of the engines. The specific placement of the fuel as it enters each chamber creates a swirl that improves the air/fuel mixture, and therefore the overall combustion process.

At engine speeds up to 3500 rpm, a double-injection process is used. In this mode, the required fuel volume is delivered in two successive injections per working stroke. The resulting benefits include faster catalyst warm-up and increased torque in the upper load range.

By forming the air/fuel mix directly in the combustion chamber, DFI contributes to engine cooling. As a result, it is possible to increase the compression ratio and with it the power and efficiency of the engine.

The direct injection process is continuously adjusted. The engine management system reads changes to throttle inputs and performance requirements and, as you drive, the air/fuel mix is monitored and adapted as required. Oxygen sensor circuits within the exhaust system provide accurate emissions control.

JENGLAND75 · #83 05-30-2009, 01:24 PM

I guess nobody here has ever owned a 993 or has known someone who has. They have issues with secondary air injection holes clogging up with carbon on engines that were lugged around like trackers. It is well know in the older air-cooled camps that you have to run these engines to keep the build up from happening. I work at a Porsche dealership and it can be a shock when someone gets a quote of $6K to pull the heads and drill out the holes and they say "well I only have 15k pampered miles on my 96 993, how could this have happened?" You try to explain that these are high performance engines designed for high RPM use.
I can just imagine what Hanns the engineer would say when someone told him about the carbon build up, "Why would someone buy a Porsche and not drive it like a Porsche? That is what Mercedes are for."
These cars are designed for the way most Germans drive, high speed Autobahn, which means under load at high RPM for long periods of time without problems.
"Porsche there is no substitute" didn't come from running down the block for your morning coffee, go and drive your cars like they are designed.

**Craig@Rennstore.com** · #84 05-30-2009, 05:46 PM

Owned a 1996 993 engine installed in a 911SC - similar yes, put the combustion path (or lack OF it) in which the gunk is deposited is completely different -

downshift · #85 06-01-2009, 09:38 AM

I owned a '95 993. I'm sure my SAI ports were clogged, but the '95 doesn't throw the CEL like the later models....

But like Craig says, the SAI ports in the 993's and the intake valves in the DFI engines are completely different. The SAI ports clog near the exhaust, and high RPMs (e.g. heat) can help prevent them from clogging. The DFI engines accumulate gunk on the intake valves, and intake valves tend to stay cooler. Well, in port injected engines, the fuel cooled the intake valves. Perhaps they will get hotter in DFI engines, without fuel to cool them.

I had an interesting thought about the accumulation of gunk on the intake valves of DFI engines the other day. In a port injected engine, gunk on the intake valves causes problems because it absorbs some of the fuel charge. The injector fires and the valve opens, but not all the fuel gets into the cylinder because some of it is absorbed in the gunk. Later, when you're in over run, that fuel gets released and burned.

Since there is no fuel to get absorbed in the gunk in a DFI engine, all it can do is impede the flow of air. I don't see a little bit of gunk on an intake valve making a huge difference in how much air can flow into the cylinder. A little bit, sure, but not a lot.

Perhaps gunk on an intake vavle in a DFI engine is not really an issue?

DFI

Direct Fuel Injection (DFI), is a new technology that Porsche states can cut fuel consumption by up to 15 percent, while increasing power by up to 13 percent. DFI cuts emissions by warming up the catalytic converter more quickly, and ensures a sharper throttle response. Better for your right foot - and the planet, then.

DFI allows much more precise measurement of fuel supply and injection at pressures up to 120 bar; it has numerous combustion modes, with different cycles for cold-starting, low-speed driving and performance driving.

As the name suggests, DFI injects fuel directly into the individual combustion chambers, instead of the intake manifold. The injector valves have an electromagnetic mechanism that controls each injection with astonishing precision, while a high-pressure pump provides the necessary pressure—up to 1,740 psi—to accompany the rapid fire of the fuel injection.

Precise geometry of the injector’s position and its spray pattern is a key factor in helping to improve power, torque and emissions of the engines. The specific placement of the fuel as it enters each chamber creates a swirl that improves the air/fuel mixture, and therefore the overall combustion process.

At engine speeds up to 3500 rpm, a double-injection process is used. In this mode, the required fuel volume is delivered in two successive injections per working stroke. The resulting benefits include faster catalyst warm-up and increased torque in the upper load range.

By forming the air/fuel mix directly in the combustion chamber, DFI contributes to engine cooling. As a result, it is possible to increase the compression ratio and with it the power and efficiency of the engine.

The direct injection process is continuously adjusted. The engine management system reads changes to throttle inputs and performance requirements and, as you drive, the air/fuel mix is monitored and adapted as required. Oxygen sensor circuits within the exhaust system provide accurate emissions control.

**JackWood** · #86 06-07-2009, 02:42 AM

Chiming in late to this discussion, but my RS4 is actually in the shop this week with excessive carbon build up.
Judging by the response from Audi UK and Europe, they are expecting excess oil consuption from blow-by to be the issue........
I'll keep you informed of any outcome.
Interesting discussion considering I am thinking of looking at a 2010 model CS soon to replace my 06 CS......never even crossed my mind to consider this "DFi Effect" in my decission making process......

DFI

Direct Fuel Injection (DFI), is a new technology that Porsche states can cut fuel consumption by up to 15 percent, while increasing power by up to 13 percent. DFI cuts emissions by warming up the catalytic converter more quickly, and ensures a sharper throttle response. Better for your right foot - and the planet, then.

DFI allows much more precise measurement of fuel supply and injection at pressures up to 120 bar; it has numerous combustion modes, with different cycles for cold-starting, low-speed driving and performance driving.

As the name suggests, DFI injects fuel directly into the individual combustion chambers, instead of the intake manifold. The injector valves have an electromagnetic mechanism that controls each injection with astonishing precision, while a high-pressure pump provides the necessary pressure—up to 1,740 psi—to accompany the rapid fire of the fuel injection.

Precise geometry of the injector’s position and its spray pattern is a key factor in helping to improve power, torque and emissions of the engines. The specific placement of the fuel as it enters each chamber creates a swirl that improves the air/fuel mixture, and therefore the overall combustion process.

At engine speeds up to 3500 rpm, a double-injection process is used. In this mode, the required fuel volume is delivered in two successive injections per working stroke. The resulting benefits include faster catalyst warm-up and increased torque in the upper load range.

By forming the air/fuel mix directly in the combustion chamber, DFI contributes to engine cooling. As a result, it is possible to increase the compression ratio and with it the power and efficiency of the engine.

The direct injection process is continuously adjusted. The engine management system reads changes to throttle inputs and performance requirements and, as you drive, the air/fuel mix is monitored and adapted as required. Oxygen sensor circuits within the exhaust system provide accurate emissions control.

Rockster · #87 06-07-2009, 12:49 PM

Originally Posted by downshift

I owned a '95 993. I'm sure my SAI ports were clogged, but the '95 doesn't throw the CEL like the later models....

But like Craig says, the SAI ports in the 993's and the intake valves in the DFI engines are completely different. The SAI ports clog near the exhaust, and high RPMs (e.g. heat) can help prevent them from clogging. The DFI engines accumulate gunk on the intake valves, and intake valves tend to stay cooler. Well, in port injected engines, the fuel cooled the intake valves. Perhaps they will get hotter in DFI engines, without fuel to cool them.

I had an interesting thought about the accumulation of gunk on the intake valves of DFI engines the other day. In a port injected engine, gunk on the intake valves causes problems because it absorbs some of the fuel charge. The injector fires and the valve opens, but not all the fuel gets into the cylinder because some of it is absorbed in the gunk. Later, when you're in over run, that fuel gets released and burned.

Since there is no fuel to get absorbed in the gunk in a DFI engine, all it can do is impede the flow of air. I don't see a little bit of gunk on an intake valve making a huge difference in how much air can flow into the cylinder. A little bit, sure, but not a lot.

Perhaps gunk on an intake vavle in a DFI engine is not really an issue?

interference with air flow into the combustion chamber. Less an issue with port injection engines cause air flow while critical is not as critical in direct injection engines.

In these the air flow wants to be precise to ensure the cloud of fresh intake air is located in area where injector will spray and where plug is.

Any deposits will almost certainly interfere with this air flow and cloud positioning (and swirling introduced by the rising piston) thus affecting engine performance.

Sincerely,

Rockster.

DFI

Direct Fuel Injection (DFI), is a new technology that Porsche states can cut fuel consumption by up to 15 percent, while increasing power by up to 13 percent. DFI cuts emissions by warming up the catalytic converter more quickly, and ensures a sharper throttle response. Better for your right foot - and the planet, then.

DFI allows much more precise measurement of fuel supply and injection at pressures up to 120 bar; it has numerous combustion modes, with different cycles for cold-starting, low-speed driving and performance driving.

As the name suggests, DFI injects fuel directly into the individual combustion chambers, instead of the intake manifold. The injector valves have an electromagnetic mechanism that controls each injection with astonishing precision, while a high-pressure pump provides the necessary pressure—up to 1,740 psi—to accompany the rapid fire of the fuel injection.

Precise geometry of the injector’s position and its spray pattern is a key factor in helping to improve power, torque and emissions of the engines. The specific placement of the fuel as it enters each chamber creates a swirl that improves the air/fuel mixture, and therefore the overall combustion process.

At engine speeds up to 3500 rpm, a double-injection process is used. In this mode, the required fuel volume is delivered in two successive injections per working stroke. The resulting benefits include faster catalyst warm-up and increased torque in the upper load range.

By forming the air/fuel mix directly in the combustion chamber, DFI contributes to engine cooling. As a result, it is possible to increase the compression ratio and with it the power and efficiency of the engine.

The direct injection process is continuously adjusted. The engine management system reads changes to throttle inputs and performance requirements and, as you drive, the air/fuel mix is monitored and adapted as required. Oxygen sensor circuits within the exhaust system provide accurate emissions control.

Rockster · #88 06-07-2009, 12:57 PM

Originally Posted by Pint of Brew

I read through this thread with interest. Some things annoy me:

1) The OP starts with some pics of valves with heavy deposits. Right. And this is a problem because? I noted the valves were still in situ, as in, not removed, so presumably they weren't replaced? Because perhaps these are pictures of heavy fouling, not of a broken engine?

2) We know nothing of this engine. We don't know how it was run, we don't know if it really does have a fault in it, we don't know if it's been run-in correctly... All we know, is it has some pictures of valves which look dirty. As far as we know, it may have faulty oil-scrape rings on some pistons causing excessive oil ingestion, which in turn is fouling. Or an O2 sensor may be broken, causing over-fuelling which is causing fouling. Or he may have chipped it with some retarded map which over-fuels far too much. Or changed an air-filter, got oil on a MAF... The list goes on.

3) A lot of you seem entirely pleased to assume Porsche don't know the difference between a Dyno and a Blender. I assure you, there are dozens of dynos, running 24/7. It is nigh-on impossible to come up with a massive defecit in an engine which nobody knew about, and even when it does it's almost exclusively due to some micro-climate (like some particularly unusual combo of oil/fuel/additive/ambient conditions). I've worked in Ford Dunton's research facility. They have 450 "cheap" dynos (few hundred thousand dollars) and eleven "expensive" ones. (just under a mill each.) and that's a research-center which only bothers with engines for the Mondeo and the Transit, which is fewer engines than Porsche has in its range. And it's Ford.

I was inclined to pitch-in this discussion, but I think I'll abstain, because we're discussing what we think is a problem, caused by something we assume to be at fault, using evidence of what we assume is an unknown finding, and suggesting it's cause of failure.

Heavy carbon deposits on valves to me says "I run my car at low load too much" and given it's allegedly a Cayenne Turbo, I'm not surprised at all. It's extremely likely the car is running 95% School Runs, at 0-15% output all day long, which using a DFI engine also means extremely low RPM, simply because DFI low RPM works just fine, thanks. Acting like you've never seen carbon deposit before doesn't mean DFI is somehow responsible for it. Before I start condemning a company which has been renowned for engine development for the last three decades plus, I'd like to take that Cayenne for a ride, run it up to the red-line a few times, and check once again to see if the deposits are still as bad. And that's only after I find out if this level of deposit actually affects the engine at all, either in its function or its longevity.

Put your pitch-forks down, you psychos! Three pics of valves isn't going to put me off Porsche any time soon.

the RMS, IMS, cylinder cracking, rod bolts weaknesses the older design engine exhibited as time went by.

I am at a point where an '09 Cayman S with new engine and possibly PDK a serious consideration (to replace my new 08 CS that was totaled in an accident and for which I'm pretty close to have collected all monies from other driver's insurance company due me). I'm not worried about valve build up.

I'm a bit more worried about the PDK and not necessarily its reliability but its suitability to my driving needs/style.

Before I make up my mind I'll test drive PDK equipped car.

But I will not have second thoughts if it happens to have DFI engine.

As I mentioned in a much earlier posting, if I can get 220,600+ miles out of my '02 Boxster engine (and original clutch) I think I can keep a DFI engine's intake valves clean.

Sincerely,

Rockster.

DFI

Direct Fuel Injection (DFI), is a new technology that Porsche states can cut fuel consumption by up to 15 percent, while increasing power by up to 13 percent. DFI cuts emissions by warming up the catalytic converter more quickly, and ensures a sharper throttle response. Better for your right foot - and the planet, then.

DFI allows much more precise measurement of fuel supply and injection at pressures up to 120 bar; it has numerous combustion modes, with different cycles for cold-starting, low-speed driving and performance driving.

As the name suggests, DFI injects fuel directly into the individual combustion chambers, instead of the intake manifold. The injector valves have an electromagnetic mechanism that controls each injection with astonishing precision, while a high-pressure pump provides the necessary pressure—up to 1,740 psi—to accompany the rapid fire of the fuel injection.

Precise geometry of the injector’s position and its spray pattern is a key factor in helping to improve power, torque and emissions of the engines. The specific placement of the fuel as it enters each chamber creates a swirl that improves the air/fuel mixture, and therefore the overall combustion process.

At engine speeds up to 3500 rpm, a double-injection process is used. In this mode, the required fuel volume is delivered in two successive injections per working stroke. The resulting benefits include faster catalyst warm-up and increased torque in the upper load range.

By forming the air/fuel mix directly in the combustion chamber, DFI contributes to engine cooling. As a result, it is possible to increase the compression ratio and with it the power and efficiency of the engine.

The direct injection process is continuously adjusted. The engine management system reads changes to throttle inputs and performance requirements and, as you drive, the air/fuel mix is monitored and adapted as required. Oxygen sensor circuits within the exhaust system provide accurate emissions control.

Pint of Brew · #89 06-08-2009, 04:10 AM

I can't agree more that prudent driving (that does not mean too soft) will help your longevity more than anything, but bear in mind if you do come buy a new car it'll have a two-year manufacturer warranty, which if you're that worried about the DFI you can extend to three for pitance. I'm extremely confident that if there is, after all, an issue with DFI a recall, fix, or alteration will cater to your every need.

It is simply impossible for a main-stream manufacturer, particularly one with such an astounding reputation for longevity, to output an engine that's anything but perfectly reliable. And even if they did, they'd support the hell out of it, simply because cars like ours live and die on their reputation, and spending 35 years to get it isn't something you toss because you can't be bothered to support.

Ever seen a 15-year old Japanese car at the trackday? Or a 20-year old French one? Because I have seen 30-year old Porsches, and "gentle" was not a term I'd use for the driver.

DFI

Direct Fuel Injection (DFI), is a new technology that Porsche states can cut fuel consumption by up to 15 percent, while increasing power by up to 13 percent. DFI cuts emissions by warming up the catalytic converter more quickly, and ensures a sharper throttle response. Better for your right foot - and the planet, then.

DFI allows much more precise measurement of fuel supply and injection at pressures up to 120 bar; it has numerous combustion modes, with different cycles for cold-starting, low-speed driving and performance driving.

As the name suggests, DFI injects fuel directly into the individual combustion chambers, instead of the intake manifold. The injector valves have an electromagnetic mechanism that controls each injection with astonishing precision, while a high-pressure pump provides the necessary pressure—up to 1,740 psi—to accompany the rapid fire of the fuel injection.

Precise geometry of the injector’s position and its spray pattern is a key factor in helping to improve power, torque and emissions of the engines. The specific placement of the fuel as it enters each chamber creates a swirl that improves the air/fuel mixture, and therefore the overall combustion process.

At engine speeds up to 3500 rpm, a double-injection process is used. In this mode, the required fuel volume is delivered in two successive injections per working stroke. The resulting benefits include faster catalyst warm-up and increased torque in the upper load range.

By forming the air/fuel mix directly in the combustion chamber, DFI contributes to engine cooling. As a result, it is possible to increase the compression ratio and with it the power and efficiency of the engine.

The direct injection process is continuously adjusted. The engine management system reads changes to throttle inputs and performance requirements and, as you drive, the air/fuel mix is monitored and adapted as required. Oxygen sensor circuits within the exhaust system provide accurate emissions control.

Rockster · #90 06-08-2009, 11:28 AM

Originally Posted by Pint of Brew

I can't agree more that prudent driving (that does not mean too soft) will help your longevity more than anything, but bear in mind if you do come buy a new car it'll have a two-year manufacturer warranty, which if you're that worried about the DFI you can extend to three for pitance. I'm extremely confident that if there is, after all, an issue with DFI a recall, fix, or alteration will cater to your every need.

It is simply impossible for a main-stream manufacturer, particularly one with such an astounding reputation for longevity, to output an engine that's anything but perfectly reliable. And even if they did, they'd support the hell out of it, simply because cars like ours live and die on their reputation, and spending 35 years to get it isn't something you toss because you can't be bothered to support.

Ever seen a 15-year old Japanese car at the trackday? Or a 20-year old French one? Because I have seen 30-year old Porsches, and "gentle" was not a term I'd use for the driver.

Porsche would issue a recall or come up with a fix or acceptable alteration?

Porsche didn't do this for IMS, cylinder cracking, rod bolt failures for the old engine.

Well, I guess in a way Porsche did offer a solution: Porsche's "solution" was a new engine design sans the IMS feature that failed way too often.

We in USA get a 4 year, 50,000 mile warranty with new car. Everyone has their own yearly mileage numbers but to let a new car warranty elapse on time and not miles is risky. I realize not everyone can drive, or wants to drive, 12.5K miles/year for 4 years just to get every mile of warranty out of their new car.

I grant you 30 year old Porsches very likely head and shoulders better than even 15 year old Japanese cars. I have no experience with cars made in France.

Sincerely,

Rockster.

DFI

Direct Fuel Injection (DFI), is a new technology that Porsche states can cut fuel consumption by up to 15 percent, while increasing power by up to 13 percent. DFI cuts emissions by warming up the catalytic converter more quickly, and ensures a sharper throttle response. Better for your right foot - and the planet, then.

DFI allows much more precise measurement of fuel supply and injection at pressures up to 120 bar; it has numerous combustion modes, with different cycles for cold-starting, low-speed driving and performance driving.

As the name suggests, DFI injects fuel directly into the individual combustion chambers, instead of the intake manifold. The injector valves have an electromagnetic mechanism that controls each injection with astonishing precision, while a high-pressure pump provides the necessary pressure—up to 1,740 psi—to accompany the rapid fire of the fuel injection.

Precise geometry of the injector’s position and its spray pattern is a key factor in helping to improve power, torque and emissions of the engines. The specific placement of the fuel as it enters each chamber creates a swirl that improves the air/fuel mixture, and therefore the overall combustion process.

At engine speeds up to 3500 rpm, a double-injection process is used. In this mode, the required fuel volume is delivered in two successive injections per working stroke. The resulting benefits include faster catalyst warm-up and increased torque in the upper load range.

By forming the air/fuel mix directly in the combustion chamber, DFI contributes to engine cooling. As a result, it is possible to increase the compression ratio and with it the power and efficiency of the engine.

The direct injection process is continuously adjusted. The engine management system reads changes to throttle inputs and performance requirements and, as you drive, the air/fuel mix is monitored and adapted as required. Oxygen sensor circuits within the exhaust system provide accurate emissions control.

**Chris S** · #91 06-10-2009, 04:22 PM

Originally Posted by Pint of Brew

Ever seen a 15-year old Japanese car at the trackday?

20 year old Miatas are pretty common at trackdays & races.

grant · #92 06-10-2009, 05:48 PM

Originally Posted by Chris S

20 year old Miatas are pretty common at trackdays & races.

So are 30 year old RX-7's and 240Z's...

zizu · #93 06-10-2009, 06:56 PM

From experience, 30 years old French car are very common in Rally racing... Actually a lot of 40 years old as well: Alpine A110 are very popular among rally drivers.

Capercat · #94 08-03-2009, 05:58 PM

Just finished reading 5 pages of this thread

Been driving a DFI VW GOLF GTI for nearly 4 years now, and what a beautiful engine! I especially like how the car immediately slows as soon as you release the throttle. Yes I've seen plenty of murky/sooty pictures on the VW forum over the years, all I can say is that no one ever had any issues with their engines.
Various tuners had produced "catch cans" but I've never really had concerns & nor did my local VW workshop mechanic regarding cleaning issues.

The day I learnt Porsche were going to use DFI in Gen II Cayman's I was sooooooo happy!!

in fact I even bought one

DFI

Direct Fuel Injection (DFI), is a new technology that Porsche states can cut fuel consumption by up to 15 percent, while increasing power by up to 13 percent. DFI cuts emissions by warming up the catalytic converter more quickly, and ensures a sharper throttle response. Better for your right foot - and the planet, then.

DFI allows much more precise measurement of fuel supply and injection at pressures up to 120 bar; it has numerous combustion modes, with different cycles for cold-starting, low-speed driving and performance driving.

As the name suggests, DFI injects fuel directly into the individual combustion chambers, instead of the intake manifold. The injector valves have an electromagnetic mechanism that controls each injection with astonishing precision, while a high-pressure pump provides the necessary pressure—up to 1,740 psi—to accompany the rapid fire of the fuel injection.

Precise geometry of the injector’s position and its spray pattern is a key factor in helping to improve power, torque and emissions of the engines. The specific placement of the fuel as it enters each chamber creates a swirl that improves the air/fuel mixture, and therefore the overall combustion process.

At engine speeds up to 3500 rpm, a double-injection process is used. In this mode, the required fuel volume is delivered in two successive injections per working stroke. The resulting benefits include faster catalyst warm-up and increased torque in the upper load range.

By forming the air/fuel mix directly in the combustion chamber, DFI contributes to engine cooling. As a result, it is possible to increase the compression ratio and with it the power and efficiency of the engine.

The direct injection process is continuously adjusted. The engine management system reads changes to throttle inputs and performance requirements and, as you drive, the air/fuel mix is monitored and adapted as required. Oxygen sensor circuits within the exhaust system provide accurate emissions control.

i a motorsports · #95 08-03-2009, 08:06 PM

The old adage still holds true- you want it to run well? run the piss out of it! the extra gas you use over the life of the vehicle will be marginal.

old school · #96 08-04-2009, 07:13 PM

Like many others, I do not see problems nor design issues with DFI. Real engine issues were displayed by badly fouled plugs in lightly driven Porsches in the 1970's. This also was a problem with 4 cam Carreras (I had a 1964 Carrera 2). These cars had to have the snot driven out of them constantly or prepare for trouble. Drive them hard and the cars were happy--just like the owners.

I have a 2009 CS with DFI and have no worries. I drive my CS at 4,000-6,000 rpm all the time. Just use lower gears and enjoy the power. Let us use lots of gasoline before the Greens/government take it away or diliute it further with "corn".

Our cars may be at the end of an era. We had best enjoy them before there are automated speed cameras on every mile of highway in the USA. Ride them hard and put them away wet.

DFI

Direct Fuel Injection (DFI), is a new technology that Porsche states can cut fuel consumption by up to 15 percent, while increasing power by up to 13 percent. DFI cuts emissions by warming up the catalytic converter more quickly, and ensures a sharper throttle response. Better for your right foot - and the planet, then.

DFI allows much more precise measurement of fuel supply and injection at pressures up to 120 bar; it has numerous combustion modes, with different cycles for cold-starting, low-speed driving and performance driving.

As the name suggests, DFI injects fuel directly into the individual combustion chambers, instead of the intake manifold. The injector valves have an electromagnetic mechanism that controls each injection with astonishing precision, while a high-pressure pump provides the necessary pressure—up to 1,740 psi—to accompany the rapid fire of the fuel injection.

Precise geometry of the injector’s position and its spray pattern is a key factor in helping to improve power, torque and emissions of the engines. The specific placement of the fuel as it enters each chamber creates a swirl that improves the air/fuel mixture, and therefore the overall combustion process.

At engine speeds up to 3500 rpm, a double-injection process is used. In this mode, the required fuel volume is delivered in two successive injections per working stroke. The resulting benefits include faster catalyst warm-up and increased torque in the upper load range.

By forming the air/fuel mix directly in the combustion chamber, DFI contributes to engine cooling. As a result, it is possible to increase the compression ratio and with it the power and efficiency of the engine.

The direct injection process is continuously adjusted. The engine management system reads changes to throttle inputs and performance requirements and, as you drive, the air/fuel mix is monitored and adapted as required. Oxygen sensor circuits within the exhaust system provide accurate emissions control.